1. Field of the Invention
The present invention relates, in general, to an instrument for implanting a prosthesis and, more specifically, to an instrument for driving a long bone prosthesis along a longitudinal axis and for rotating the long bone prosthesis about the longitudinal axis.
2. Background Art
A long bone prosthesis, such as a femoral hip prosthesis, typically includes an elongated stem for insertion into a long bone canal; a neck attached to the proximal end of the stem; and a head attached to the proximal end of the neck for articulating with a coacting prosthesis or with natural structure. The head may be integrally attached to the neck or may be removably attached to the neck through a Morse taper or the like. The neck may be angled relative to the longitudinal axis of the stem. The angle between the neck and the longitudinal axis of the stem may vary from prosthesis to prosthesis. This is especially true for custom manufactured prostheses (i.e., prostheses manufactured based on radiographs or the like to fit specific patients).
To implant such long bone prostheses, a surgeon normally prepares the medullary canal of the long bone to receive the elongated stem of the prosthesis, and then inserts the stem into the prepared canal. The prosthesis must be properly positioned within the canal so that the articulating surface of the head will ultimately mate correctly with the articulating surface of the coacting prosthesis or natural structure, etc. It is normally necessary for the surgeon to use force to drive the prostheses into the prepared canal, especially for so-called press-fit prostheses as opposed to cemented prostheses. Simple punch-like drivers are sometimes used to seat such press-fit prostheses. Prostheses may be provided with indentations in a proximately directed surface thereof for receiving the distal ends of such punch-like drivers.
Although proper preparation of the medullary canal may guide the prosthesis to seat where the surgeon wants, a tight fit or variations in the 3-dimensional geometry may urge or rotate the prosthesis into some undesirable position. In order to insure such proper positioning, the surgeon may be required to rotate the stem within the canal, etc. In such cases, the prosthesis should be rotated or otherwise moved into the desired position with care to insure that the prosthesis is not damaged. A mere scratch on an articulating surface of the prosthesis or on the taper of the prosthesis can cause the prosthesis to be unusable.
The design, dimension and geometry of long bone prostheses vary greatly from one prosthesis to another. This is especially true for custom implants where numerous dimensions, angles, etc., of the implant are allowed to change in order to optimize implant fit for each individual patient. Not only do length, width, and geometry change, the neck angle can also change as required to restore best possible anatomic function. Such variations in design, dimension and geometry, etc., have created the need for similar variations in tools used to implant such prostheses.
Nothing in the known prior art discloses or suggests the present invention. More specifically, nothing in the known prior art discloses or suggests a surgical instrument for driving and rotating a prosthesis and including, in general, a shaft having a first end for engaging the prosthesis, having a second end, and having an axis between the first and second ends; and grip means adjustably attached to the shaft so that the relative position between the shaft and the grip means can be adjusted, and for gripping the neck of the prosthesis so that force applied along the axis of the shaft toward the first end of the shaft will drive the prosthesis into the bone and so that rotational force applied to the axis of the shaft will rotate the prosthesis.